XML 54 R41.htm IDEA: XBRL DOCUMENT v3.10.0.1
ASSET RETIREMENT OBLIGATION: (Details)
$ in Millions
 3 Months Ended 6 Months Ended 12 Months Ended
Mar. 31, 2018
USD ($)
Jun. 30, 2018
USD ($)
item
Jun. 30, 2017
USD ($)
Dec. 31, 2017
USD ($)
ASSET RETIREMENT OBLIGATION:        
Period after which successive reviews are required by the law (in years)   5 years    
Accepted value of the Lima office building   $ 36.9    
Cumulative guarantee amount   $ 32.3    
Number of units with future closure costs recognized as an asset retirement obligation | item   3    
Changes in estimates $ (5.2) $ (15.6)   $ (11.6)
Asset retirement obligation activity        
Balance at the beginning of the year 222.5 222.5 $ 216.5 216.5
Changes in estimates $ (5.2) (15.6)   (11.6)
Payments     (0.3)  
Accretion expense   6.2 6.6  
Balance at the end of the year   213.1 $ 222.8 $ 222.5
Mexico        
Environmental cost        
Plant demolition and soil remediation budgeted cost   $ 66.2